Projection Operator in Surgical Robot Kinematics for Low-DOF Tools

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Robotic systems for minimally-invasive surgery face challenges in converting user commands with six degrees of freedom into joint motions for tools with fewer degrees of freedom, leading to undesirable and unintuitive behavior due to infeasible motion directions.

Innovation Solution

Incorporating a projection from the greater degree of freedom of user input commands to the lesser degree of freedom of surgical tools within the inverse kinematics, which accounts for the limited degrees of freedom of the tool, allowing for feasible motion solutions and minimizing differences in joint position changes based on feasible and infeasible poses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If inverse kinematics is solved without projection for tools with less than six DOFs, then the computational process is simpler, but the motion commands become infeasible and unintuitive

Engineering Contradiction:

Improvecomputational process complexityVSAvoidmotion command feasibility

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

A projection operator is introduced as an intermediary component between the user command space (6 DOF) and the tool command space (less than 6 DOF). This projection operator maps the full 6 DOF user commands onto the feasible subspace of the tool's actual DOFs, ensuring that the resulting motion commands are both computationally derived and physically feasible for the tool to execute.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If a general inverse kinematics solution is used for all tools, then the system is more versatile, but it cannot account for tools with limited degrees of freedom

Engineering Contradiction:

Improvesystem versatilityVSAvoidmotion accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The system dynamically adapts the projection operator based on the specific tool's DOF characteristics. Different tools (scissors, endoscope, ultrasound scalpel) have different DOF configurations, and the projection operator is configured accordingly for each tool type, allowing the general framework to precisely accommodate the specific motion capabilities of each instrument.

Inventive Principle:

Principle #15Dynamics

3Ease of operation

If projection is incorporated into inverse kinematics for tools with less than six DOFs, then the motion commands become feasible and intuitive, but the computational process becomes more complex

Engineering Contradiction:

Improvemotion command feasibilityVSAvoidcomputational process complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The projection operator modifies the command parameters by transforming 6 DOF user commands into the appropriate parameter space for the tool's actual DOFs. This parameter transformation ensures that the commanded motions are expressed in terms that the tool can physically execute, converting infeasible arbitrary 6 DOF commands into feasible reduced DOF commands.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12076099B2Projection operator for inverse kinematics of a surgical robot for low degree of freedom tools

Publication Date: 2024.09.03 AURIS HEALTH INC

AI summary

For teleoperation of a surgical robotic system, the control of the surgical robotic system accounts for a limited degree of freedom of a tool in a surgical robotic system. A projection from the greater DOF of the user input commands to the lesser DOF of the tool is included within or as part of the inverse kinematics. The projection identifies feasible motion in the end-effector domain. This projection allows for a general solution that works for tools having different degrees of freedom and will converge on a solution.